Explanation
Galvanisation is a metallurgical process primarily used to protect iron and steel structures from corrosion (rusting). It involves the application of a protective layer of a specific metal over the iron substrate.
Detailed Analysis:
- Zinc (Correct Answer): Galvanisation specifically refers to the coating of iron or steel with Zinc. The most common method is hot-dip galvanizing, where the iron is submerged in molten zinc.
- Mechanism of Protection: Zinc protects iron in two ways:
- Barrier Protection: It forms a physical barrier that prevents moisture and oxygen from reaching the iron surface.
- Sacrificial Protection: Zinc is more reactive than iron (placed higher in the electrochemical series). Consequently, if the coating is scratched or broken, the zinc oxidizes (corrodes) in preference to the iron, thereby protecting the underlying metal. This is known as sacrificial protection.
- Other Metals:
- Chromium and Nickel: These are often used in electroplating to provide a shiny finish and corrosion resistance (e.g., in car parts or taps), but this process is not called galvanisation.
- Copper: Copper is less reactive than iron. If iron is coated with copper and the coating is breached, the iron would rust faster due to galvanic action.
Key Takeaway:
Galvanisation is the specific process of coating iron with Zinc to prevent rusting through barrier and sacrificial protection.